Apple fruit moth - Plant volatiles mediate colonization of a new host

Insect herbivores use plant volatiles to recognize and to efficiently locate their host plants. Female and male insects perceive these signals via specialized olfactory receptor neurones, and use them to discriminate food sources, rendez-vous sites or larval foodplants from the background chemical environment. Latest findings suggest a key role of host volatiles in host plant discrimination, and host race formation and sympatric speciation in herbivorous insects.

 

Many host races or recently diverged insect species are available for study, but differentiation and adaptation of the sensory system to the respective hosts may obscure the mechanisms which once led to the initial host shift. The apple fruit moth Argyresthia conjugella is accordingly a species which invites attention, as it recurringly and unsuccessfully colonizes apple Malus domestica every few years.

 

Flowering and fruitsetting of its preferred host rowan Sorbus aucuparia(Rosaceae) fluctuates in spatial synchrony in Fennoscandia. When too few rowanberries are available for egg-laying, A. conjugella females invade closeby orchards, where they oviposit on apple, which is not suitable for complete larval development.

 

We have studied the hypothesis that olfactory cues mediate attraction of apple fruit moth to its larval hosts. We show that attraction to plant volatiles co-occurring in rowan and apple may account for the observed host switch from rowan to apple.

 

Funding

Geir Knudsen (Bioforsk Ås) is funded by the Norwegian Research Council

 

Personnel

Marie Bengtsson, Peter Witzgall

 

Collaboration

Geir Knudsen, Gunnhild Jaastad, Sverre Kobro (Bioforsk)

 

Selected references

Bengtsson M, Bäckman A-C, Liblikas I, Ramirez MI, Borg-Karlson A-K, Ansebo L, Anderson P, Löfqvist J & Witzgall P (2001) Plant odor analysis of apple: antennal response of codling moth females to apple volatiles during phenological development. Journal of Agricultural and Food Chemistry 49, 3736-3741

 

Bengtsson M, Jaastad G, Knudsen G, Kobro S, Bäckman A-C, Pettersson E, Witzgall P (2006) Plant volatiles mediate attraction to host and non-host plant in apple fruit moth, Argyresthia conjugella. Entomol exp appl 118, 77-85

 

Knudsen GK, Bengtsson M, Kobro S, Jaastad G, Hofsvang T, Witzgall P (2006) Discrepancy in laboratory and field attraction of apple fruit moth Argyresthia conjugella to host plant volatiles.